Final answer:
The hair root is the translucent tissue containing the richest source of DNA, located within the hair follicle. It is the only living part of the hair, ending at the hair bulb in the dermis, making it valuable for DNA analysis.
Step-by-step explanation:
The translucent piece of tissue surrounding the hair shaft near the root that contains a rich source of DNA is known as the hair root. This part of hair, located within the hair follicle, consists of living cells which make it a valuable source for DNA analysis. The hair root ends deep in the dermis at the hair bulb, which is surrounded by the hair papilla containing blood capillaries and nerve endings that supply it with nutrients and signals for growth.
The hair follicle is made up of three concentric layers of cells—the internal root sheath, the external root sheath, and the glassy membrane. Specifically, the internal root sheath and the matrix cells of the hair bulb adjacent to the hair follicle are the areas from which DNA can be most successfully extracted. This is because the hair matrix contains a layer of mitotically active basal cells, which are the source of the hair's keratinocytes and carry a rich source of genetic material.